\\[-1.8ex] Soil Heterogeneity & $-$0.552$^{***}$ & $-$0.534$^{***}$ & $-$0.514$^{***}$ & $-$0.470$^{***}$ \\ 
  & (0.194) & (0.193) & (0.167) & (0.165) \\ 
\\[-1.8ex] 
Observations & 23,322 & 23,322 & 23,064 & 23,064 \\ 
R$^{2}$ & 0.339 & 0.341 & 0.344 & 0.353 \\ 
